I love making and collecting interlocking 3D puzzles. They have traditionally been made from wood and can look quite beautiful as sculptures, as well as being great fun to try and solve.

There are, however, some problems with using wood.

For simple puzzles, wood is an excellent material to practice on

For more complex puzzles a high degree of craftsmanship is required to make puzzles that look good and work well

Wood is naturally hygroscopic and changes in size with the humidity; this can make puzzles looser and tighter at different times of the year

Professionally made wooden puzzles can be very expensive – I recently paid about $50 for a professionally made wooden cube I had designed

That’s why I started experimenting with 3D printing as a way of producing high-quality puzzles at affordable prices.

Printed puzzles are never going to be as cheap as mass-produced versions because of economies of scale but for small-scale production of unusual and complex puzzles there is real potential. They will never be as aesthetically pleasing as wooden puzzles but puzzles are primarily there to be played with – as the best puzzle resource on the Internet puts it, Puzzle Will Be Played ….

One type of 3D printing involves a process known as selective laser sintering (SLS) of powdered plastic. The resulting white plastic pieces are accurate to a tenth of a millimetre, strong and resilient. The Shapeways 3D printing service charges flat rate of $1.68 per cm³ which makes it very easy to adjust the size of the puzzle to reach a compromise between cost and usability.

It’s arrived! All the pieces have finally come together and at last I have my own puzzle factory complete with its own shop.
The final piece of the puzzle was put in place by those fine people over at Shapeways in Eindhoven with their web-based and very reasonably priced 3D printing service. So, just for the record, here’s how the process works.

Step 1
Inspiration for a new puzzle comes from playing with LiveCubes. Alternatively, one of the many excellent puzzles at ‘Puzzle Will Be Played‘ provides a ready source of pieces ripe for making.

Step 2
The physical puzzle made from LiveCubes is modelled in Burr Tools and becomes a virtual puzzle inside the computer. Burr Tools is an absolutely fantastic free program that can not only solve most puzzles once you have created them, but can also export industry-standard STL files compatible with most 3D printers.

Step 3
Cleaning up the STL files is an important step, otherwise the pieces may be unprintable. This is done in another piece of free software called Blender. Blender is a very nice 3D modelling program which also includes a range of tools. Removing duplicate points and non-manifold faces (don’t worry about it) makes the cleaned up models ready for the next stage.

Step 4
Finished models can be uploaded directly to Shapeways through their website. Within a couple of minutes an email is returned to you telling you whether their printer can read the file or not. If there’s a problem it’s usually just a case of going back into Blender and seeking out the offending points or edges. Once it’s printable it’s simply a matter of choosing a material (White, Strong and Flexible works well for puzzles) placing an order and waiting for the pieces to be delivered to your door 10 days later.

Well that’s the theory anyway. There was just a little bit of fine tuning to do and the tweaking and testing took several more weeks.

Exporting STL files from Burr Tools

When you export STL files from Burr Tools there are 3 parameters that have to be set – Cube size, Bevel and Offset. These are the values that need to be carefully selected in order for the process to work.

Export STL

Cube size

This value is the size in millimetres (my preferred units – just tell Shapeways what units you choose) of one unit cube and the default value is 10. Now 10 mm equals 1 cm, so your unit cube will have a volume of 1 cubic centimetre. Shapeways prices are all quoted per cubic centimetre and are around $2 to $3 depending on your choice of material. But a 3 x 3 x 3 cube has a volume of 27 cubic centimetres and a 4 x 4 x 4 cube has a volume of 64 cubic centimetres. Getting the unit Cube size right will make a vast difference to the price of the puzzle.

Bevel

The default value is 1, which is 10% of the default Cube size. The bevel is important to stop the edges of cubes from snagging on each other as they slide past. It needs to stay in proportion to the size of the cube or it will look very odd. Choose your Cube size first and then set the Bevel to 10% of that.

Offset

This is the depth shaved off each face of the cube to ensure that the printed puzzle will move and not get stuck. The default value is 0.1 and I would strongly suggest leaving it at this value, independent of the value of your cube size. This is where I went wrong initially. I scaled down my Cube size, Bevel and Offset keeping them all in proportion but this resulted in the offset value being significantly less than 0.1 mm and the pieces just got jammed together.

Getting my first working cube back was so exciting! It worked really well and at a very affordable price. I set about creating my own Shapeways shop straight away and had it up and running the next day. Inspired by the tiny size of my first working cube and the name of this blog, I settled on the name ‘microcubology’. Creating a new microcubology account on YouTube gave me somewhere to demonstrate my puzzles in action. Now I just need a few more puzzles in the shop window before I sit back and wait for the orders to come rolling in!

OK. So it hasn’t taken the world by storm yet, but right around the world there is a small hard-core group of metagrobologists whose passion is designing, making and solving puzzles.

No, not jigsaw puzzles, or crossword puzzles, but real solid 3-dimensional objects that can be put together, taken apart, disentangled, sequentially interlocked, re-orientated and generally solved.

I’ve been a puzzle fan since my childhood and have fond memories of both of my grandfathers having small collections of dexterity puzzles and curious objects. In my teenage years I discovered Martin Gardner’s column in Scientific American magazine and was enthralled by his regular features on puzzles that could be made at home.

The first wooden cube I ever made was a tiny version of Piet Hein’s Soma Cube, made by gluing together 27 white single unit cubes from a set of Cuisenaire Rods that my parents had bought us to help us with our maths homework.

Over the years, I gradually improved my woodworking skills and progressed to making burr puzzles of ever increasing complexity. My favourite wooden puzzle type has always been the interlocking 4 x 4 x 4 cube which has numerous variations and levels of difficulty. Making and solving wooden puzzles was (and is) great fun but the ultimate goal for me was to design my very own puzzle.

This seemed like just wishful thinking until, in 2003, I discovered LiveCubes – like Lego for puzzle designers. I bought a starter pack of cubes from their shop and before long I had my first two creations.